It is well known that an aircraft will build up a significant static charge on its external surfaces while flying due to impact of the aircraft with rain, snow, sleet, dust, ash or fog resulting in triboelectric charging due to particle impact, this being the major contributor to aircraft charging in general. This type of charging has been labeled P-Static charging by those working in the field of aviation and is a distinct and different process of electrical charging phenomena than, for example, the process of generating static charge by the rubbing of two materials against each other such as a glass rod against wool or fur. To a lesser degree, static charge may also be acquired on an aircraft due to its movement through the earth's electrical and magnetic fields, when in the vicinity of electrical storms or by that generated by the aircraft's propulsion system either jet engine or propeller type. For purposes of this application, the invention is for the local harvesting of P-Static charge, its conversion locally to useful low voltage electrical power, and the use of that electrical power by locally collocated electronic devices and a wireless transmitter. The other types of aircraft static charge mentioned above will also be captured by the invention if they are found to be locally available too.
It has been noted by others that a large aircraft such as a Boeing 707 aircraft will charge in-flight to a level of several hundred thousands volts or higher if the aircraft does not have means to discharge the static electrical charge that is building up and accumulating on the aircraft. If the aircraft can not rid itself of static charge, the voltage potential will build up from low to higher and higher levels and a point will be reached where corona discharge occurs directly from the aircraft or its appendages and the resulting electrical energy that is radiated from these high voltage discharges will interfere with aircraft communication and navigation systems. Since 1949 and even earlier, apparatus has been developed which is attached to the aircraft and prevents serious corona discharge from occurring. One example of such a discharger is that described in U.S. Pat. Nos. 2,466,024 and 2,466,311 by W. C. Hall which discharges the static charge to the surrounding atmosphere. These early efforts focused on methods to discharge the unwanted and bothersome static charge at low enough voltage potentials that interference due to corona discharge is reduced or nearly eliminated. The inventions of W. C. Hall utilized a discharger employing either fibrous surfaces of non-conducting wicks moistened with a liquid of suitable electrical conductivity or fiber wicks made semi-conducting by incorporation therein of finely dispensed conducting materials or by impregnating them or coating them with microscopic metal particles. Such wicks were mounted on the aircraft, trailing in a downstream direction, at its wing tips and trailing edges as well as on the horizontal stabilizer and vertical tail. Improvements in existing discharger designs and the development of new designs for static charge dischargers which diminish corona discharge effects have continued to this day with over fifty related patents being granted since 1949.
As a result of recent developments in technology, electronic devices capable of performing certain tasks have been reduced substantially in physical size and power usage. For example, electronic units that previously weighed several kilograms, took up several cubic meters of space, and used amperes of electrical power to perform a given task are now replaced by electronic chips or micro-electro-mechanical (MEMS) devices weighing mere grams with their volumes measured in cubic millimeters and power in milliamperes. These reductions in weight, size and electrical power requirements now allow the realization of innovations not previously believed possible.
As an example of an invention made possible through utilization of the new technology, the present inventor filed a Utility patent application Ser. No. 11/804,701 for an ice detection system in which the ice sensor is collocated with all supporting electronics and data processor in a small, thin, pliable patch mounted to the exterior surface of an aircraft. The patch does not increase the aircrafts drag significantly or interfere with the flowfield about it since the miniature size of all components selected for use in the subject ice detection system allows such a patch to have a vertical height measured in millimeters. A major element used in that invention is an impedance measurement chip, No. 5933 by Analog Devices Inc, which measures 6.2 mm in width, 7.8 mm in depth and 2.0 mm in height and which draws only 10 milliamperes or 25 milliamperes depending on whether it is operating in the Standby Mode or Operational Mode; size and power levels unbelievable just a few years ago. By being able to collocate all components of the ice detection system together, wire and coaxial cable lengths between components are much reduced with significant savings in weight and cost as well as diminished detrimental cable effects in the measured data.
Another example of a device that is available for use as an externally mounted, low power consumption sensor on an aircraft is the Akustica AKU2000 MEMS microphone on a chip whose frequency range is 100 Hz to 10,000 kHz and which is fabricated on a 3.0 mm wide by 3.65 mm deep by 0.5 mm high chip which operates from a 3 volt supply (5 volt maximum) and consumes less than 130 microamperes. Such a device could be used to monitor sound levels radiated by an aircraft during takeoff, flight and landing and used to determine the physical locations on the aircraft of major noise sources. Based on this example, along with the previous one and others not discussed, DC electrical power requirements for realistic advanced miniature electronic devices for use on aircraft fall in the range from approximately 0.1 milliamperes to 25 milliamperes at voltages in the range from 3 volts to 5 volts with an additional 10 milliamperes needed to power the wireless transmitter again at an operating voltage in the range from 3 volts to 5 volts.
Though the electrical power requirements are small for the two examples considered above, they presently require that electrical power be provided to them through wire runs connected internally from the aircraft power system to them; these wire runs having lengths from a few meters to over thirty meters in length depending on the size of the aircraft being instrumented and the placement location chosen for the devices on the aircraft. They also require that the aircraft be wired internally with wiring that carries back information and/or measured data to the interior of the aircraft for use or recording. A significant improvement in the acceptance and use of such miniature measurement devices would result if the wires needed to supply electrical power to the devices (and wires for return of data) could be eliminated and needed electrical power provided by local means. If local power generation were possible, it would allow such devices to be located anywhere on the aircraft without consideration of how wires would be guided to them through the interior of the aircraft; resulting in a significant savings in time, materials and installation costs in preparing for their usage. It is well known that any internal modifications to an aircraft such as new wire runs are time consuming to install and excessively expensive to incorporate. What is needed and what would be a significant improvement over what can be achieved today is a way to produce and store electrical energy locally for use by these miniature, low power electronic devices.
Such an improvement is now offered by the present invention which collects P-Static charge locally along with other static charge if also available locally, stores it locally in a rechargeable capacitor (or rechargeable battery) storage unit and provides electricity, after local power conditioning, directly to nearby devices as needed. For power requirements of the device that are low in comparison to the P-Static Electrical Power Systems capability, the power is provided continuously. If the power requirements of the device are large with respect to the local P-Static Electrical Power Systems capability, the device is provided power on an intermittent basis. Use of a P-Static Electrical Power System on an aircraft or on an electrically ungrounded object subjected to the wind and charged P-Statically will now be considered in more detail.
The invention consists of the following parts from input to output: a dielectric charge generator, an upstream overvoltage protection circuit, a relay/solid state switching circuit connected downstream to an excess charge discharger or to a rechargeable capacitor and/or battery storage unit, a DC-DC and/or DC-AC down converter, a downstream overvoltage protection circuit, a device or devices to be powered, a wireless transmitter and a lightning protection unit.
The P-Static invention discussed herein initially stores the electric charge at high voltage in a rechargeable capacitor (or rechargeable battery) storage unit. It then converts the energy to usable voltage and power through a DC-to-DC and/or DC-to-AC step down converter. The maximum amount of energy stored in the P-Static power system depends on the maximum voltage capability selected for the rechargeable capacitor (or rechargeable battery) storage unit as well as the total capacitance of the assembled capacitors or the number of rechargeable batteries used and whether the rechargeable capacitor (or rechargeable battery) is recharged while in use. Implicit in the present invention is the fact that information or data measured and/or processed by the local low power consumption sensor or electrical device is transmitted wirelessly from the sensor or device back to the interior of the air vehicle or to the interior of the ungrounded object for use or recording; thus eliminating the need for wires in the return direction.
The invention provides a major improvement in the design of an experiment or an application on an aircraft in that it eliminates the requirement that electrical wiring be installed internally in the aircraft to provide electrical power to each and every device as well as eliminating the wiring necessary to carry signals back from the devices. Thus installation of devices is simplified; devices may be mounted anywhere on the air vehicle or ungrounded object and installation costs are substantially reduced. The electrical charge that is harvested is called P-Static charge and is normally considered undesirable and unwanted. If P-Static charge is allowed to build with time and not dumped from the aircraft or diminished in some way, it causes electrical discharges to occur on the aircraft and the electrical noise resulting from those discharges interferes with communication and navigation equipment as well as other aircraft electronic equipment. Because P-Static charge causes such problems, much effort is normally expended to discharge it from the aircraft to the surrounding atmosphere using static dischargers attached to the aircraft. The present invention, for the first time, utilizes aircraft generated P-Static charge in a useful manner as an energy source.
As to prior art, a thorough and extensive search of prior art on aircraft P-Static charging was conducted and no patent was found that used P-Static charge in any manner other than to get rid of it nor, in particular, in any useful manner as done in the present invention. All prior patents for aircraft P-Static charge treated it as something to eradicate rather than something that might be put to good use. Nowhere in the prior art was a suggestion found that aircraft P-Static charging could be used for any useful purpose such as energy harvesting as considered in the present invention.